1. Field of the Invention
This invention concerns retrievers for submerged objects, particularly retrievers comprised of a canister containing water activatable pellets that form a gas when exposed to water to force a floatable cap off of the cannister such that it will surface and mark the position of the submerged object. This invention also relates to improved seals for such canisters to permit the ingress of fluid into the container through an aperture while selectively sealing the aperture against the escape of gas which is evolved by the reaction between the water and the water activatable pellets inside the container.
2. Description of the Prior Art
U.S. Pat. No. 2,785,420 discloses a device for indicating sunken objects which is comprised of a cylindrical container in which a water activatable pellet is placed. Water enters the container by dissolving a water dissolvable seal, and gas evolved by a chemical reaction between the water and pellet forces a floatable cap off of the canister and to the surface of the water, thereby marking the position of the submerged object. This device most dramatically illustrates the drawbacks of the prior art in that the water activatable pellet can react with atmospheric moisture which enters the container without the dissolvable seal first being dissolved. Once the chemical reaction between the pellet and atmospheric moisture has taken place, the device is not functional, but a person using the device does not know it is not functional until an object is submerged beneath the water and the buoy cap does not rise to the surface. This is obviously much too late a time at which to remedy the problem.
Another drawback to the structure disclosed in U.S. Pat. No. 2,785,420 is that once the water dissolvable seal is dissolved, nothing prevents the evolving gas on the interior of the canister from merely escaping from the canister instead of forcing the plug out of the end of the cylinder and to the surface of the water. The disadvantages of this drawback are that the buoy may not be sent to the surface and the submerged object cannot be located.